Add all ingredients except the ginger beer into a shaker with ice and shake until well-chilled.
Pour into a highball glass over fresh ice.
Top with the ginger beer and stir gently.
Garnish with an orange twist.
*Tarragon syrup: Add 1 cup sugar and 1 cup water into a saucepan. Bring to a boil, reduce heat, and simmer until sugar is dissolved. Remove from the heat, add 12 tarragon leaves, and let steep for 20 minutes or until desired flavor is reached. Store in refrigerator up to 2 weeks.